Thermal effects are generally used in the field of skin care to supplement and/or amplify product efficacy.
Heat acting on the skin causes the pores to open, which improves the efficacy of a cosmetic composition applied on the skin. Thus, heating effects can be used notably in deep-cleansing products, such as exfoliating products containing abrasive particles, or in relaxing products. Heat will reinforce the sensation of deep cleansing or of relaxation. These heating effects can also be utilized in combination with actives or cosmetic agents which are rendered more active under the effect of heat.
Cooling effects are generally used in cleansing products when we wish to reinforce the sensation of freshness and the toning effect. They can also be used in care products, notably moisturizers for enhancing the sensation of hydration.
In general, these thermal effects are obtained by means of exothermic or endothermic compounds used as such or more generally used in anhydrous compositions containing exothermic or endothermic compounds. Most often, these anhydrous compositions contain a large amount of oils or of polyols and notably glycols.
Thus, document DE-A-10009252 describes cleansing gels containing at least 40% of polyols and water-soluble salts as particles. Document EP-A-1106164 describes solid cosmetic compositions, comprising a powder based on solid particles of expanded polymer and a binder containing oil and one or more agents that are capable of releasing heat, such as polyols and zeolite. Document EP-A-966956 describes pulverulent anhydrous compositions containing a powder based on solid particles of expanded polymer and a binder containing one or more agents capable of releasing heat, such as polyols and zeolite.
However, these compositions have poor cosmetic properties owing to the high levels of polyols which make the compositions sticky and heavy, or high levels of oils, which make them very greasy. Furthermore, very often it is useful to thicken these media for suspending the salts or zeolites required for producing the thermal effect. However, this operation is difficult owing to the poor swelling of the gelling polymers in these media.
Moreover, these compositions may impose formulation constraints, restricting the range of formulation to components that are soluble or dispersible in glycols or oils. These drawbacks are sometimes overcome by using two-compartment packaging articles enabling the heating composition to be separated from the other ingredients that are used in the composition, but are incompatible with the heating composition. Attempts are made to avoid using this complex packaging.